Black-Faced Blenny

Like all triplefin-blennies, T. delaisi has three dorsal fins and can hence easily be distinguished from members of the families Blenniidae (1 dorsal fin) and Gobiidae (2 dorsal fins) that have a similar lifestyle and general appearance. It has a peaked head and short tentacles above the eyes.⁠

T. delaisi inhabits 2 disjunct areas: 1. the western Mediterranean Sea and adjacent parts of the Atlantic Oceans from north to the British Isles and south of Casablanca and Morocco, 2. western tropical Africa north to Senegal and the Macaronesian islands.

T. delaisi is a carnivore that mainly feeds on small crustaceans, such as Harpacticoids, Tanaidaceans, Caprellidae, and Amphipods. It cannot bite pieces out of its prey and thus cannot eat prey larger than its mouth.⁠ Defecation takes 1 to 2 s.⁠

Prior to the capture, T. delaisi looks at the prey item for several seconds; meanwhile the first dorsal fin rhythmically twitches about twice per second. The capture is achieved by a sudden inhaling movement, which sucks the prey into the mouth. If the prey is attached to the substrate, it is torn loose by a sideward movement of the head.

Overall the territorial period of the males lasts from beginning of February until beginning of September, but the average duration of the territorial period per male was 47.1 days (in Corsica )⁠. Male T. delaisi show territorial behaviour for 2 consecutive years. Spawning takes place from mid of March until June.⁠

The male territories are located on the lower side of overhanging cliffs and rocks and have a diameter of around 1 metre (3.3 ft). If two territories are visually hidden from each other their centres can be as close as 0.5 metres (20 in). Within the territory a smaller area of 20 by 20 centimetres (7.9 in × 7.9 in) is used for nesting. Male T. delaisi are able to find their territories from distances up to 200 m away.⁠